Remove `Bucket` and `RawTable` that are hard to use safely
Remove `Bucket` and `RawTable` that are hard to use safely

This removes the following methods in favor of better alternatives:
- `RawTable::erase_no_drop` => Use `RawTable::erase` or
  `RawTable::remove` instead.
- `Bucket::read` => Use `RawTable::remove` instead.
- `Bucket::drop` => Use `RawTable::erase` instead.
- `Bucket::write` => Use `Bucket::as_mut` instead.

rust-lang/hashbrown,rust-lang/hashbrown